According to the paper, "several people distributed unsigned tracts on the square," located in a political center of Tehran close to Iran's former imperial parliament building.

Qods said "mercenary foreign media" had induced the youth to gather on the square in order to spark unrest and trigger social violence," while the fundamentalist Jomhuri-Eslami blamed "foreign media and counter-revolutionary elements."

Communiqués said to have been issued by the unknown organization affirmed that the gathering was being held to "denounce dictatorship in Iran."

So far, officials have given no information on the demonstration or the arrests. Among those detained was a photographer from the AFP bureau in Tehran, Behrouz Mehri.

Several other journalists, including some from the state news agency IRNA, were also apprehended but were later released following the demonstration called by the "Student Branch of the Movement for Iran's National Salvation."

Jomhuri-Eslami said several Islamic militia groups had gathered later Saturday on Baharestan Square, chanting slogans against the United States and in favour of Iran's supreme leader Ayatollah Ali Khamenei.

Pro-reform groups close to President Mohammed Khatami have said that there was no reformist rally scheduled for Saturday and called on people not to take part in any demonstration.

The interior ministry has also confirmed that no authorization had been given for a rally on Saturday - TEHRAN (AFP)